This invention relates generally to magnetic disc recording apparatus utilizing recording disc housed in cartridge enclosures. More particularly, it relates to such recording disc cartridges which substantially enclose the recording disc with a selectively openable and closable aperture providing access for the recording and playback transducer when the cartridge is in place in a disc drive unit. Even more particularly, the invention relates to a closure mechanism for use with such cartridges and disc drive units.
In magnetic disc recording units various types of recording media are used. These types include fixed discs which are made a substantially permanent part of the entire recording system, and removable discs, which permit interchange of blank and recorded media for varying requirements. There are various types of removable media, including disc packs which, when installed on the disc drive unit, have their protective housing substantially removed to provide access to the various recording surfaces. Another popular and well known type of removable media is that of the disc cartridge, incorporating one or a plurality of recording discs within an enclosing cartridge housing, which housing includes a selectively openable aperture through which the recording and playback transducers are introduced to the disc recording surfaces. Such a cartridge housing is designed to remain in place around the recording disc whether the disc is removed from the drive unit for storage or is installed in an operable relation with the drive unit.
Recording disc cartridges necessarily provide some form of selectively openable closure for selectively covering and uncovering the aperture through which the recording and playback transducers are introduced into the cartridge. This is necessary because it is important and desirable to maintain the cartridge closed when it is removed from the protective environment of the disc drive unit to avoid contamination of the recording surfaces by foreign matter, such as dust and fingerprints. It is thus important that this closure be opened when the cartridge is inserted into the unit and closed when it is removed therefrom.
In the prior art various types of closures have been utilized, including pivoting doors which swing upwardly or to the side under the actuation of mechanisms associated with the disc drive, and other doors which slide transversely to the side of the aperture upon insertion of the cartridge into the drive unit. Where space is at a premium, the pivoting doors are disadvantageous, since they require sufficient room to swing open. The various types of transversely moving doors have reduced the space requirement but have suffered from various disadvantages stemming from their designs. One type of such closure has employed a flexible, foil-like door which is pulled off to the side and around a corner by the insertion of a portion of the disc drive unit into the cartridge, with a spring urging the closure back to its closed position upon withdrawal of the cartridge from the drive unit. Another approach utilizes a rack and pinion arrangement in which a part of the drive unit forms a rack engaging and rotating a pinion within the cartridge by the insertion of the cartridge into the drive unit, with this rotation both serving to roll the closure door away from a closed position and also winding a coiled, clock-type spring, the wound spring providing the force to urge the door back to a closed position.
While these prior art arrangements have provided the basic necessary functions, they have suffered from numerous disadvantages. These disadvantages stem, to a large extent, from the use of spring biasing arrangements to effect closure and retention of the door structure in a closed position. Any weakness in the spring may cause the door to close less than fully, thus permitting contaminants inside. This problem is exacerbated by the fact that the door, in its substantially closed position, approaches the limit of effort of the spring such that the final closing force and force retaining the door closed may be relatively low. This problem also has rendered the door mechanism susceptible to inadvertent opening and thus undesired potential entry of contaminants into the interior of the cartridge.